A medicament delivery device, such as an injector, is often arranged with a container holder to allow operations to be carried out on the container, for instance displacement within the injector housing during skin penetration, expulsion of medicament by a plunger acting on the stopper in the container, penetration of the septum using a needle and replacement of container. Because of tolerances, manufactured containers vary in size, which may result in the position of the container within the holder being somewhat affected during handling of the device. For instance, displacement of the container may occur as a result of penetrating the septum of the container with a needle or by sudden impact forces to the housing of the device. If the container is not exactly positioned in relation to the holder, the stroke length of the plunger rod—and consequently the dosage set by the user or the manufacturer of the device—will not be exactly correlated to the actual position of the container, resulting in the wrong dose being delivered. Also, movement of the container within the holder may lead to a higher risk of breaking the container due to impact forces between the holder and the container.
A number of prior art solutions to container holders are known:
U.S. 2007/0021718 A1 describes a spring for use as a supporting device between a container and a housing in order to firmly position the container within the housing. The spring is not attached to the container holder but wedged between an insert and the container, or attached to the housing of a power pack. Therefore it is not suited to secure the container to the container holder on its own.
EP 0 941 133 B1 discloses a cartridge assembly intended to key a cartridge to a certain type of injection pen in order to prevent cross-use of different cartridges and pens, which could result in the wrong drug being used or the patient receiving the wrong dose. Various embodiments describe a cartridge assembly where the cartridge is secured in a cartridge holder that is adapted for a specific cartridge and for a specific pen. Also, the rigid construction using cooperating threaded holder parts to secure the cartridge could lead to damage to the cartridge if too much force is used to join the parts.
WO 2010/097116 A1 describes a container holder for securely holding a container wherein the holder includes a support for the shoulder of the container in the front end, flexible arms exert a compressive radial force on the sides of the container and hooks at the rear end keep the container inside the container once it has been inserted in the container holder and pushed past the hooks. There is no resilient member that holds the container in the same position in relation to the holder, i.e. due to tolerances the container may be slightly axially displaced during handling of the device.
U.S. 2006/0030819 A1 discloses a cartridge container arranged with inwardly directed resilient tabs that apply a radial compressive force on the cartridge to align and to hold it in proper orientation and to hinder axial and radial movement of the cartridge inside the cartridge container during loading. The use of resilient tabs allows accommodation of cartridges of different sizes, but no compressive force is used to bias the cartridge axially.
EP 2 021 054 B1 describes an injection device wherein a syringe may be moved from a retracted position to an extended position for discharging its contents and wherein the syringe is held by a syringe carrier. The syringe is held in the carrier by arms arranged with lugs and dampers that grip the rear surface of a flange of the syringe in order to minimize the risk of the syringe breaking by impact force such as caused by sudden movement, i.e. during extension or retraction of the syringe. No precaution is taken to fix the syringe in a predetermined position inside the carrier.
Therefore, there is a need for a device that can securely keep the container in one predetermined position in relation to the container holder in order to be able to deliver a set dose in a safe and reliable way without damaging the holder. With regard to cost and complexity the device needs to be easy to manufacture and to implement in existing devices. The resulting device must also be simple and intuitive for the end user to operate.